29 September, 2021

GPS Clock published

Version 1 of my GPS Clock is here, as open source software for the Arduino Mega. It has some 22 19 different display screens showing time, location, solar and lunar positions and rise/set times. It shows UTC time as received from the GPS satellites and local time where it automatically adjust for summer time. The initial screen, no. 0, is this:

23 August, 2021

Finally figured out the moon

I’ve been working on a GPS-controlled Arduino clock for some years and had set myself the goal of showing time for moonrise and for moonset for the present day. That turned out to be much harder than I had thought.

Finally, over the last few weeks I managed to adapt lunarCycle.c to Arduino and get it to work as shown in the display here. My ambition is now eventually to publish this project on GitHub as I’ve had several requests for it.

The display here shows local time and date, moon phase on line 2, present moon elevation and moon azimuth on line 3, and the next rise time of the moon and at which position on the final line. Follow label ‘Arduino clock’ below for more posts about this clock.

10 July, 2021

Coordinated WSPR band hopping with the QRPLabs U3S

There is a recommended sequence for multi-band transmission on WSPR. It is given in the K1JT WSPR documentation. If enough receivers follow this sequence, then presumably letting WSPR transmissions also follow it, will increase the chance of detection. 

The recommended band hopping sequence cycles through 10 bands over a 20 minute period according to this table:

Band (m)   160  80  60  40  30  20  17  15  12  10
UTC Minute  00  02  04  06  08  10  12  14  16  18
            20  22  24  26  28  30  32  34  36  38
            40  42  44  46  48  50  52  54  56  58

The multi-band U3S is capable of adhering to such a sequence. There are however three considerations that need to be taken into account. 

14 April, 2021

Learning the hard way that plastic TO-92 is affected by humidity

I've had my APRS temperature station running since 2012. It is based on a DS18S20 sensor that just sticks out of a window. However, after some time it started to give too high readings, and after having replaced it several times I found out that I needed to waterproof it better. It seems that the TO-92 plastic housing, shown here to the right, somehow was influenced by humidity.

I wasn't able to find waterproofed DS18S20 sensors, but I could find ones with DS18B20. I got one and connected it, but it only showed -1 C regardless of weather. The software in the Opentracker USB was not able to read it, although I have Arduino programs that can read both.

07 April, 2021

Now active via the International Space Station

I happened to set my 2m receiver to the APRS (Automatic Packet Reporting System) frequency of the International Space Station (ISS), 145.825 MHz, and lo and behold stations in Central and Southern Europe started to appear. This is not rocket science, but for me it's a first. (Well actually the ISS is a kind of rocket ...)

Here in Oslo, using the local APRS service, I can also receive Swedish and Danish stations when conditions are good, but never Spain, Italy, Greece, Romania, Ukraine, Russia or Turkey. When a message appeared from NA1SS itself, the station onboard the ISS, I felt that I had really nailed it (see image). But ISS had more in store for me.

03 March, 2021

QRPLabs 25 MHz TCXO performing well in the U3S

I have tried several oscillators in the U3S QRSS/WSPR transmitter from QRPLabs. First an analog devices DDS, then a Silicon Labs oscillator chip running from an ordinary 27 MHz crystal, and then QRPLabs own oven controlled oscillator. I thought I had managed to control the drift when I got the oven controlled oscillator. But then after a while it started drifting again. I didn't want to go through its rather cumbersome calibration procedure once more so I gave it up recently when the TCXO module became available. This tiny module is shown in the first image.

23 January, 2021

Eleven and 87 year sunspot cycles

It is well known that the sunspots vary over an eleven-year cycle. As the sunspot number increases, the ionosphere is more ionized and radio propagation on the high shortwave bands from about 10 - 30 MHz. Also, the higher the sunspot number, the more likely is the appearance of Northern Lights.

Here's spectral analysis of the monthly sunspot numbers from 1750-2020. First I show Fourier based spectrogram analysis. The y-axis is frequency or inverse years and there are arrows marking 11 years as well as the Gleissberg cycle of about 87 years. Note how the 11 year cycle has split into two periods since the 50's. There is a weak subharmonic at 5.5 years also. Due to the 90 year analysis window length, the time scale ends 45 years before 2020, i.e. in 1975. 

19 October, 2020

Longwave AM transmitter based on the XR-2206

Some years ago I described some AM transmitter experiments for the longwave band from 150 to 300 kHz. A transmitter that worked over a few meters was based on an XR-2206 function generator IC. Instead of building it from scratch as that first article indicated, I ended up purchasing and modifying the "Geekcreit® XR2206 Function Signal Generator DIY Kit Sine Triangle Square Output 1Hz-1MHz" from Banggood. 

That kit is not intended for AM modulation as the modulation input, pin 1, is grounded. It therefore needed these modifications: